1. Field of the Invention
This invention relates to an exercise stand for a bicycle, and more particularly to a bicycle exercise stand which holds the driving wheel of the bicycle clear of the floor surface and exerts magnetic force on the driving wheel so that bicycle pedaling exercise simulates actual cycling.
2. Description of the Prior Art
Using a bicycle as an indoor training apparatus, by holding it in such a way that it cannot move, and pedaling, has been being done for several decades. For this training, a stand which raises the driving wheel (the rear wheel) of the bicycle clear of the floor surface and holds it in such a way that it is free to rotate is necessary.
Prior art exercise apparatuses of this kind include for example those disclosed in U.S. Pat. No. 4,768,782 and U.S. Pat. No. 4,969,642. These stands comprise a horizontally aligned pair of supports mounted in such a way that they project upward from a frame formed of a front/rear pair of tubular members assembled in parallel with each other. The driving wheel (the rear wheel) of the bicycle is placed on a resistance-providing drum rotatably mounted on the frame. With the bicycle in this position, the pair of rotation shafts which project out from both sides of the hub are respectively rotatably fitted into a fixed sleeve and a movable sleeve which extend toward each other from the supports. In this way, the rear wheel is held on the drum by the two sleeves, and a load caused by the resistance of the drum is put on the rear wheel as it is rotated on the resistance-providing drum by the pedaling of the user. As a result, by pedaling with a treading effort corresponding to the load being put on the rear wheel, the user can achieve an exercise effect.
However, in U.S. Pat. No. 4,768,782, while the fixed sleeve is held projecting inward with a fixed length set in advance, the construction of the movable sleeve is such that the portion projecting out of the support can be lengthened and shortened by the operation of a screw. One of the rotation shafts of the rear wheel is fitted into the fixed sleeve, and the movable sleeve is lengthened and fitted onto the other rotation shaft to grip the hub.
In this operation, to set the bicycle on the stand, the user holds the upper part of the rear end of the bicycle with both hands so that the rear wheel, which has been placed on the resistive force generating drum, does not become separated from the drum. At the same time, it is necessary for the user to lengthen the movable sleeve and fit it onto the rotation shaft by operating the screw with another hand stretched down to the lower part of the rear end of the bicycle. Because of this, the task of setting the bicycle on the stand is awkward.
In U.S. Pat. No. 4,969,642, the fixed sleeve is constructed in almost the same way as that described above, and the movable sleeve is constructed in such a way that it can be lengthened and shortened by the operation of a lever. Because of this, it is necessary for the user to position the rear wheel of the bicycle on the drum while holding the bicycle up with one hand, and stretch the other hand to the lower part of the rear of the bicycle to operate the lever. Thus, with the stand of U.S. Pat. No. 4,969,642, as with the stand disclosed in U.S. Pat. No. 4,768,782 mentioned above, the task of setting the bicycle on the stand becomes awkward.
Bicycle exercising stands that have been marketed in the past also include the type shown in FIG. 17. A pair of tubular members 101, 102 which constitute the frame 100 of this stand extend parallel to each other, and two pairs of leg parts 103, 104 (of each pair, only the leg part on the near side is shown in the drawing) which extend diagonally upward are mounted on the ends of the tubular members 101, 102. The leg parts 104 are pivotally supported at the upper portions of the leg parts 103. A pair of holding members 105 (only one is shown in the drawing), for firmly holding the hub 111 of the rear wheel, are mounted at the top ends of the leg portions 103.
A loading device 106 for providing a load resistance corresponding to the rotational speed of the rear wheel 111 is mounted on the tubular member 101. As shown in FIG. 18, the resistance-providing device 106 is made up of a resistance generator 107, having a rotary shaft 108, and a small-diameter drive cylinder 109 which is mounted on the rotary shaft 108 and makes contact with the tire 112 of the rear wheel 111. The resistance generator 107 is constructed in such a way that a pair of permanent magnets are disposed facing each other on either side of a metal rotary disk which is fixed to the rotary shaft 108, and the rotation of the rotary disk along with the rotation of the rotary shaft produces eddy currents in the rotary disk and puts a load on the rotation of the rotary shaft.
After the rear wheel 111 of the bicycle 110 has been placed on the drive cylinder 109, by firmly holding the hub of the rear wheel 111 between the two holding members 105, preparation of the bicycle 110 for exercise is completed. A load resistance corresponding to the rotational speed of the rear wheel 111 rotating along with the rotation of the pedals 113 of the bicycle 110 is generated in the generator 107, and that load resistance is transmitted to the rear wheel 111 through the drive cylinder 109.
In the laoding device 106 described above, when the tread pattern of the tire is of the rib type, continuous in the circumferential direction, the drive cylinder 109 and the tread pattern of the tire are in surface contact at all times as the drive cylinder 109 rotates along with the rotation of the rear wheel 111. As a result, if the rotation of the rear wheel 111 is roughly constant, the rear wheel 111 is continuously provided with a roughly constant load resistance through the drive cylinder 109, and the user can do the pedaling exercise smoothly. And, because the drive cylinder is in surface contact with the tread pattern of the tire at all times, the noise generated by the contact between the two is not great.
However, in the loading device 106 discussed above, the outer diameter of the drive cylinder 109 is small. Therefore, as shown in FIG. 18, when the tread pattern 112a of the tire 112 is for example a block type, like the tire of a cross-country bicycle, the drive cylinder 109 does not make surface contact with a plurality of tread patterns 112a mutually adjacent in the circumferential direction of the tire 112 simultaneously. Because of this, as the rear wheel 111 rotates, the corner of the pattern 112a which comes after the pattern 112a which is in surface contact with the drive cylinder 109 collides with the drive cylinder 109. As a result, there is the problem that unevenness occurs in the load resistance with which the rear wheel 111 is provided through the drive cylinder 109, it becomes impossible for the user to do the pedaling exercise smoothly, and the contact between the tire 112 and the drive cylinder 109 produces a loud noise.